Select value in another table if reference is found - sql

Question

Alright, I'm pretty desperate. This is my first time using StackOverflow (I've always find all my answer but not this time). Please Community I need your help cause I'm not a SQL wiz. (I'm using Access).
I have 3 tables "User", "Type" and "User_update". I want to get the value from the "User" table but if there's an update for that user in the "User_update" table I would like to have the value from the "User_update" table instead and the date of the update. :-/
TABLE "USER"
id | user | type_id
--------------------
0 | bibi | 1
1 | toto | 1
TABLE "TYPE"
id | type
-----------
0 | admin
1 | normal
TABLE "USER_UPDATE"
id | user_id | type_id | date
-----------------------------------
0 | 1 | 0 | 9/3/2015
Would like to get something like this:
user | type | date
--------------------
bibi | normal |
toto | admin | 9/3/2015
Hope you guys can help!

Answer 1

I don't know Access, but here's an ANSI SQL answer:
select coalesce(uu.user, u.user), t.type, uu.date
from user u
left join user_update uu on u.id = uu.id
join type t on t.id = coalesce(uu.type_id, u.type_id)
The LEFT JOIN is there to read from user_update if a matching row is found. COALESCE returns the first non-null value, so if a user_update has been found that value is returned, otherwise user value is returned.
NOTE: In ANSI SQL date and user are reserved words, so these may need to be delimited, e.g. "date" or perhaps [date].
Access attempts:
select coalesce(uu.user, u.user), t.type, uu.date
from (user u
left join user_update uu on (u.id = uu.id))
join type t on (t.id = coalesce(uu.type_id, u.type_id))
Or perhaps:
select coalesce(uu.user, u.user), t.type, uu.date
from type t
join (user u
left join user_update uu on (u.id = uu.id))
on (t.id = coalesce(uu.type_id, u.type_id))

Answer 2

As someone new to access, I would recommend you design most of your queries using the "Design View". You want to left join the USER table on both tables, using the USER.type_id = TYPE.id and USER.user = USER_UPDATE.user
The following SQL should accomplish what you want, returning the "USER_UPDATE" record should it have a value, otherwise it will return the "TYPE" record.
You will need to look to see if there can be multiple records in "USER_UPDATE" for the same user, depending on your use, the return of multiple records may not be what you are looking for, you will need to build a select query to return only the most recent record in "USER_UPDATE"
SELECT USER.id, USER.user, USER.type_id, IIf([USER_UPDATE].[type] Is Null, [type].[type],[USER_UPDATE].[type]) AS user_type, USER_UPDATE.date
FROM ([USER] LEFT JOIN TYPE ON USER.type_id = TYPE.id) LEFT JOIN USER_UPDATE ON USER.user = USER_UPDATE.user;